The present invention relates to a photographic film cassette, and more particularly, to an improvement on a light trap fabric which traps light entering the cassette through a film passage mouth.
Presently, a photographic film cassette containing a roll of 135-type (35 mm wide) photographic film is used most widely. This film cassette is constituted by a light-tight cylindrical cassette housing provided with a film passage mouth, a spool rotatably contained in the cassette housing, and a film coiled on the spool. The film leader is maintained in a state in which it protrudes from the film passage mouth. When loading the film cassette into a camera, the film leader is brought into engagement with a threading member of the camera. By driving the threading member, the film is pulled out from the cassette and fed to a film take-up chamber so as to be wound onto a take-up spool in this chamber.
A light trap fabric (commonly called plush) is attached inside the film passage mouth in order to trap light which enters through the film passage mouth into the cassette housing. A number of light trap fabrics are known, including a woven fabric with pile threads as described in Japanese Utility Model Publication No. 37-21388, a knitted fabric with pile threads woven therein as described in Japanese Utility Model Publication No. 61-34526, a fabric made by inlaying pile threads directly in a film passage mouth as disclosed in Japanese Utility Model Publication No. 37-4453 and Japanese Patent Laid-open Publications Nos. 53-105222 and 57-190947, and a non-woven fabric as disclosed in Japanese Utility Model Laid-open Publication No. 51-127737.
If a pile fabric having pile threads is used as a light trap fabric, the directions of pile threads can become disorganized during processes such as dying and brushing. In some cases, pile threads will be inclined in the film rewinding direction, i.e. the inside of the cassette housing. In this case, the light trap fabric will resist the force of film advancement, so that the film cannot be advanced smoothly. Also, the surface of the film may be scratched.
As described in U.S. Pat. Nos. 4,832,275, 4,834,306, 4,848,693, and 4,846,418, and Japanese Patent Laid-open Publications Nos. 1-306844, and 1-306845, a self-advancing film cassette has been proposed in which the film is contained completely within the cassette, and the film leader is advanced to the film passage mouth upon rotation of the spool. With a film cassette of this type, whose film leader is positioned initially within the cassette, if there is a large resistance against film advancement as described above, the film may be bent within the cassette.